Black currant (nomenclature: Ribes. nigrum) is a plant that belongs to genus saxifraga (or genus hydrangea depending on classification). Because of the distinctive flavor, taste, acidity and the like of black currant fruit, black currant has been employed as a starting material for jams, fruit juice, alcohol beverages and the like for example in Europe. The black currant is edible in an uncooked state although it is not employed in that manner often due to its strong acidity. Fresh juice just squeezed from black currant has a solids concentration (Bx) of about 10%, and contains about 20 to 30% by weight of organic acids such as citric acid and malic acid on the basis of solid matters, and about 30 to 50% by weight of monosaccharide on the basis of solid matters. This makes acidity and sweetness excessively strong. Therefore, only a small amount thereof could be added to, for example, drinks such as juice, and gelatinous foods. To other foods, it was not added at all.
Fruit juice concentrate is commercially available as a starting material for these drinks. This is provided by squeezing fresh juice from fruit, followed by the removal of only water with the aid of, for example, an uncharged reverse osmosis membrane to prepare an approximately six-fold concentrate. In general, in the case of six-fold concentrates of apple juice, orange juice and the like, dilution with water, the volume of which is six times greater than that of the fruit, produces 100% fruit juice as a reduced product from fruit juice concentrate. However, in the case of black currant juice concentrate, as with the case of the fresh juice, the concentrate comprises about 20 to 30% by weight of organic acids such as citric acid and malic acid on the basis of solid matters, and about 30 to 50% by weight of monosaccharide on the basis of solid matters, and thus, acidity is excessively strong. Therefore, it was impossible to produce 100% fruit juice from black currant.
It is known that black currant contains an anthocyanin as a coloring component. As shown in FIG. 1, the structure of anthocyanin is a glycoside of anthocyanidin, which is the aglycon. Black currant anthocyanin is mainly composed of delphinidin and cyanidin as the anthocyanidin.
As J. Banaszczyk et al. have reported in Fruits Process 6 (8), 321-325, 1996, the content of the black currant anthocyanin at Bx. 11 is not more than 600 to 800 mg/l regardless of variety. This indicates that 100% fresh juice of freshly-squeezed black currant contains only 0.06 to 0.08% by weight of black currant anthocyanin. Because the Bx of the juice is about 11, the content of black currant anthocyanin is 0.55 to 0.73% by weight on the basis of solid matters. According to this report, storage of the juice for 14 weeks decreases the amount of the black currant anthocyanin to 300 mg/l. Further, the content of the black currant anthocyanin greatly varies depending on crop year. By the subsequent year, content decreased to 80 mg/l, that is, one tenth of the previous year (0.07% by weight on the basis of solid matters). As indicated above, the amount of the black currant anthocyanin in the fresh black currant juice greatly varies depending on the storage condition and crop year, i.e., 0.07 to 0.73% by weight on the basis of solid matters. This indicates that foods containing 1% or more by weight of black currant anthocyanin on the basis of solid matters did not exist. Furthermore, black currant 100% fruit juice is not suitable for drinking due to its extreme acidity so that a neutralizer, a sweetener and the like are usually added to the juice. For this reason, the amount of the black currant juice added in the actual production of juice is generally much less. For general quaffable black currant juice, the content of black currant anthocyanin is generally not more than 0.5% by weight on the basis of solid matters although it depends on the amount of neutralizer or sweetener added. Thus, the content of black currant anthocyanin in conventional foods derived from black currant was not more than 0.73% by weight on the basis of solid matters, not more than 0.08% by weight on a product basis, for the 100% fruit juice which was unsuitable for drinking, and not more than 0.5% by weight on the basis of solid matters for general quaffable juice.
Jams are produced by using frozen fruit as starting materials with the addition of a large quantity of, for example, sugar and pectin. Therefore, in general, the content of black currant anthocyanin is up to about 0.3% by weight on the basis of solid matters, and up to about 0.2% by weight on a product basis. It is a matter of course that the content of organic acids and sugar is larger than usual fruit juice.
“Explanatory notes on the list of food additives other than chemically synthesized products” describes a coloring agent of black currant although it is hardly commercially available these days. According to this, the coloring agent is produced by “squeezing from black currant belonging to family saxifraga or extracting with the aid of water”. This coloring agent is produced merely by extraction, and the content of black currant anthocyanin, organic acids, and the saccharide content is equivalent to those of general fruit juice. Properties thereof are described as “red to dark red or dark blue liquid or a paste or a powder”, indicating that a powdery coloring agent existed. However, this powdery coloring agent is also produced by pulverizing the liquid coloring agent obtained by extraction with the addition a binder and the like. Regarding the black currant anthocyanin component on the basis of solid matters, this is equal to or less than that of fresh fruit juice.
Conventionally, anthocyanin has had a problem in its stability, that is, it decomposes when the fruit juice is used in drinks such as juice.
Fruits containing a large quantity of anthocyanin include blueberries. Some varieties of blueberries contain not less than 2% by weight of blueberry anthocyanin on a dry fruit basis. Therefore, in some food industries, blueberry anthocyanin is extracted with the aid of an organic solvent and the like from, for example, fruits or fruit juice concentrate to utilize it as a coloring agent for foods [“Shokuhin kogyo (THE FOOD INDUSTRY)” issued Aug. 30, 1997].
Blueberry anthocyanin comprises: 5 kinds of anthocyanidins, i.e., cyanidin, peonidin, delphinidin, petunidine, and malvidin; and 15 types of anthocyanins, i.e., combinations of 3 types of sugar moieties, i.e., glucose, arabinose, and galactose. The main component is reported as malvidin, and the content of delphinidin and cyanidin is about 10 to 20% by weight [“Shokuhin to kaihatsu (up-to-date food processing) vol. 31, No. 3, p 5-8].
As described above, properties, hues, pharmacological functions and the like of blueberry anthocyanin would be different from those of black currant anthocyanin since anthocyanidin compositions contained therein differ significantly from one another.
Only an infinitesimal quantity of blueberry anthocyanin is needed for coloring. Therefore, currently employed coloring agents contain only about 2% by weight of the anthocyanin on the basis of solid matters, i.e., equivalent to fruit juice concentrate. Further, such coloring agents for foods are extracted with an organic medium so that a distinctive flavor thereof is lost.
The content of these blueberry anthocyanins is merely for use in coloring agents. Therefore, in for example drinks using a coloring agent extracted from blueberry described in Japanese Patent Laid-Open No. 84564/1997, the amount of the coloring agent added is 0.025 to 0.05% by weight, which is an infinitesimal quantity, 0.00625 to 0.0125% by weight, in terms of the amount of blueberry anthocyanin. Conventionally, foods containing a large quantity of blueberry anthocyanin did not exist.
As described above, the amount of black currant anthocyanin contained in black currant is very small, not more than about 0.7% by weight on the basis of solid matters. Black currant anthocyanin has hitherto been regarded unsuitable as a starting material for a coloring agent. Thus, it is a matter of course that there was no food containing a large quantity of black currant anthocyanin. For this reason, a black currant anthocyanin material, which can be added to food in a large amount, has been strongly desired.
In Europe, blueberry anthocyanin has hitherto been employed as a pharmaceutical. However, anthocyanin derived from other fruits was not very well known possibly because of its anthocyanin content.
When blueberry anthocyanin is employed as a pharmaceutical, a larger quantity of the anthocyanin has to be taken compared to the case where blueberry anthocyanin is employed as a coloring agent. Therefore, anthocyanin has to be purified, and a process therefor is disclosed in, for example, Japanese Patent Laid-Open No. 99090/1991. Disclosed therein is a process wherein an aqueous solution containing a bisulfite ion prepared by adding sulfur dioxide, sodium hydrogensulfite, sodium pyrohydrogensulfite and the like is added to a fruit or an extract thereof, separation is performed using a nonionic polymeric resin under neutral pH conditions, sulfurous acid is eliminated using an inert gas, and anthocyanin is then extracted with an organic medium immiscible with water (for example, butanol and amyl alcohol). However, this process is not directed to food applications but to pharmaceutical and cosmetic applications. In Japan, however, the Food Sanitation Law prohibits the use of organic media such as butanol and amyl alcohol, and thus, they cannot be used for foods. Use of harmful sulfurous acid gas (described in vol. 3 of “Dictionary of Biochemistry”, NIHON KAGAKU DOJIN) is not preferable for fear of its remaining in products. Therefore, the anthocyanin according to Japanese Patent Laid-Open No. 99090/1991 was only applicable for pharmaceuticals, but not applicable for foods. This had led to the need of compositions for foods containing a large quantity of anthocyanin in the food industry.
Japanese Patent Publication No. 50633/1983 describes a process for producing anthocyanin for foods. This process exemplifies grapes or products obtained from grapes, and is carried out by a combination of an ultrafilter membrane having a cutoff point in the range of a molecular weight of 1,000 to 70,000, at a molecular weight of about 20,000 under optimal conditions, with an uncharged reverse osmosis membrane having salt retention rate of 30 to 99%, preferably 50 to 90% in the case of NaCl. Reverse osmosis membranes used in this process are of an uncharged type, the salt retention rate thereof is greatly different from that of the present invention, and the membrane is used for separation of water only, thus this process greatly differs from the process of the present invention. In the examples, extraction is carried out with a solution containing sulfurous acid anhydride and alcohol. In actual operation, use of an organic medium and evolution of sulfur dioxide is of concern. According to measurement of the optical density of anthocyanin, when the ultrafilter membrane is utilized, optical density is concentrated from 7,150 to 15,020, i.e., a concentration factor of 2.1 times compared to before filtration. When the uncharged reverse osmosis membrane is utilized, optical density is concentrated from 7,150 to 7,400, i.e., the concentration factor of 1.03 times compared to before filtration. This indicates that the ratio of concentration and purification is low. There is no description on the content of grape anthocyanin. However, even if an assumption is made that the content of grape anthocyanin in fruit juice before purification is 0.5% by weight on the basis of solid matters, according to the process in Japanese Patent Publication No. 50633/1983, the content of the grape anthocyanin in the extract obtained by ultrafiltration after purification is 1.05% by weight, and the content of grape anthocyanin in the concentrate obtained through the uncharged reverse osmosis membrane is about 0.52% by weight on the basis of solid matters. This indicates that the content is not high, and the quality is unsatisfactory.
According to the process disclosed in Japanese Patent Publication No. 31225/1985, anthocyanin is extracted with the aid of a sulfur dioxide solution from grapes, cranberries, blackberries and the like and separated by ultrafiltration. As described in Example 1 of the publication, in this process, 200 to 500 ppm of sulfur dioxide (sulfurous acid gas) remains in the final product. According to this process, the anthocyanin content of the final product is described to be about 1.0% by weight.
Japanese Patent Laid-Open No. 223756/1984 describes a process wherein anthocyanin is purified using an ion-exchange resin or an absorptive resin. However, there is no description on the concentration of anthocyanin in the prepared coloring matter. The purification process is directed to the removal of sludge generated in drinks.
Starting materials for anthocyanin described in these known documents are mostly blueberries (Bilberry, Vaccinium. myrtillus) which contain a large quantity of anthocyanin in the fruit thereof, or grapes which are inexpensive as fruits. There is no description concerning black currant.
The present inventors have keenly searched for a process for producing compositions for foods containing a large quantity of black currant anthocyanin without using harmful substances and found an effective process for the first time. Surprisingly, foods and drinks, comprising the black currant anthocyanin produced according to this process, have visual function improvement effect, blood fluidity improvement function, and blood pressure lowering function. They are found to be effective as functional foods and drinks.
Visual functions are important functions accounting for a large part of sensory function. However, lowered visual function has become a problem these days. For those who operate computers and the like including personal computers and word processors, it is widely known that the rate of complaints of asthenopia is significantly higher than those who do not operate computers.
In optic organs, continuous operations concentrating on near points including computer work and computer games, maintain stress on the ciliary muscle which is a smooth muscle. This leads to reflact value of myopia, that is, pseudomyopia. This is reported in Japanese Journal of Opthalmology, 72, 2083-2150 (1968). It is an established theory that this pseudomyopia some day becomes myopia. Substances for preventing or improving lowered refracting power of crystalline lens or pseudomyopia caused by computer operations are required.
As the number of senior citizens increases in society, the problem of lowered visual acuity in senior citizens is growing. In our daily lives, there has been a rapid increase in situations where there are complaints of lowered visual acuity. For example, as the number of senior drivers rapidly increases, the occurrence of problems, for example, dazzling going into or out of tunnels and lowered visual acuity at night which are problems not associated with young drivers, has become significant.
On the other hand, many people commonly use eyeglasses and contact lenses to correct their visual acuity. The use thereof, however, is inconvenient in their lives. In particular, people, who suffer from myopia in combination with presbyopia, astigmatism or the like, have serious inconveniences so many people hope for recovery of function.
Conventionally, attempts have been made at curative mechanisms for the improvement or recovery of visual function by utilizing visual acuity recovery training such as watching distant points, surgery, pharmaceuticals and the like. None of these process, however, is very common.
Several studies have been already made on pharmaceuticals having a visual function improvement or recovery function. For example, phosphoramidon is the subject of a patent application as an endothelin converting enzyme inhibitor having curative effects on asthenopia (Japanese Patent Laid-Open No. 143099/1997). For example, taurine, menthol, neostigmine methylsulfate, and VE acetate are subjects of a patent application as instillations for improving asthenopia (Japanese Patent Laid-Open No. 143064/1997). Also subjects of patent applications are, for example, an emollient for strain of ciliary muscle (Japanese Patent Laid-Open No. 133225/1995), a therapeutic agent for asthenopia using cyclopentolate hydrochloride (Japanese Patent Laid-Open No. 149517/1990), and a solid pharmaceutical using adenosine sodium triphosphate (Japanese Patent Laid-Open No. 308232/1989). Most of these substances, however, are instillations that are pharmaceuticals used as eye drops. Although administration of these pharmaceuticals can temporarily relieve symptoms, chronic symptoms would not be relieved. Therefore, substances having effects on improving visual function or substances for preventing the lowering of visual function through routine food ingestion are desired. In fact, there are several reports on foods functioning to improve visual function. However, effects were measured only for subjective symptom so that scientific and objective evaluation of effects using equipments has not been carried out. For example, a triglyceride comprising docosahexaenoic acid, α-linolenic acid, and γ-linolenic acid is reported in Japanese Patent Laid-Open No. 255417/1995 wherein the evaluation is carried out by merely questioning the subjects in respect of their subjective symptoms in which subjects are simply divided into two groups to conduct a test. Therefore, individual differences among subjects are likely to develop. Also, because the number of participants “n” is as small as 5, and statistical processing is not particularly conducted, actual effects cannot be said to have been scientifically evaluated.
Regarding substances for maintaining eye function, those containing a viscera concentrate of mirror carp, a ginseng extract, Pseudoginseng, powders of pearl shell, a chrysanthemum, and a cassia seed extract described in Japanese Patent Laid-Open No. 97690/1993, supposedly have effects. Substances that are supposed to be active ingredients include a wide variety of substances and their effects are not specified. According to the examples in the publication, since the evaluation was made only by a questionnaire, it is hard to say the effects are scientifically verified.
In Japanese Patent Laid-Open No. 97691/1993, compositions having functions for improving eye diseases and functions for maintaining eye mechanisms are subject of a patent application, and proposed active substances include a shark fin extract, a viscera concentrate of mirror carp, a ginseng extract, Pseudoginseng, powders of pearl shell, chrysanthemum, a Chinese matrimony vine extract, and a cassia seed extract. These proposed substances lack scientific grounds as with the previously described publication.
Also subjects of patent applications as products, having functions for recovering visual acuity, are health foods for eyes comprising, as essential ingredients, the leaf portion of Japanese persimmon and the fruit of guava, as described in Japanese Patent Laid-Open No. 59217/1987. According to this invention, as with the above-described invention, the visual acuity is subjectively examined and effects are hardly scientifically verified.
Food materials having mechanisms for improving visual function, which are recently gaining people's attention, include the blueberry. According to this report, a double blind cross over experiment for a group comparison test is carried out for 20 patients who have subjective symptoms of mental fatigue and asthenopia with the control group being provided with a placebo. Unlike the evaluation process of foods cited in the above-described literature, an evaluation using equipment is additionally carried out. The results thereof show an improvement in subjective symptoms and in a flicker test. However, the results show no improvement in: for example, subjective epidoptometry, i.e., 30 cm visual acuity and 5 m visual acuity; and objective epidoptometry, i.e., a measurement of refracting power “THE FOOD INDUSTRY” issued Aug. 30, 1998). Further, the flicker which is the equipment used is described in The Journal of Japan Accident Medical Association, 1992, vol. 40, No. 1, p. 12-15: “a flicker test is a process for evaluating asthenopia and is related to fatigue in brain cortex, and cerebral excitability, but not related to an optic center”. According to the description on page 221 of “Practical Opthalmology” vol. 18, issued by Bunkodo, “a measurement of central flicker is effective in evaluating a disorder of tertiary neuron such as ophthalmic nerve disease, (omitted), the flicker is unaffected by refractive error or mild optic media”. The flicker test measures cerebral functions rather than visual functions. More specifically, regarding the effect of blueberries, the evaluation is presumably made on the effect attained by recovery of central function, in particular, cerebral function rather than improvement of visual function.
As described above, no food materials have hitherto been known where an effect on improving the visual function was scientifically verified using proper equipment.
The present inventors have found that foods, containing black currant anthocyanin for foods purified by the process described below, have scientifically verified mechanisms for improving visual function.
Anthocyanidins, being aglycon of anthocyanin, have been employed as pharmaceuticals in Europe, and are known to have pharmacological properties valuable in treating peripheral vascular disease (Japanese Patent Laid-Open No. 81220/1991). However, those having a scientifically verified visual function improvement effect have not been developed as foods.
Starting materials for anthocyanin described in patent specifications for pharmaceuticals containing anthocyanin are mostly blueberries (Bilberry, Vaccinium. myrtillus) which contain a large quantity of anthocyanin in the fruit thereof or grapes which are inexpensive as fruit. The black currant has not been employed. Therefore, pharmacological effects of black currant anthocyanin have been hardly studied at all. This may be because the content of black currant anthocyanin in black currant is a very small quantity of not more than about 0.7% by weight on the basis of solid matters. The present inventors have found a novel function of black currant anthocyanin, which has hitherto been left out of account. Because the blueberry anthocyanin affects the central nerves rather than visual function, functions and mechanisms thereof could be different from those of black currant anthocyanin.
In recent years, the spread of life-style related diseases, attributable to opulence and lack of exercise, has come to be regarded as a problem, and particularly, matters associated with the circulatory system such as an elevated blood pressure, hyperglycemia, and an increase in neutral fat and cholesterol in blood have come to be regarded as serious. In particular, adverse affects created by neutral fats and cholesterol cause an increase in blood viscosity, thereby preventing blood from rapidly flowing through blood vessels. This increases vascular resistance which may in turn cause the elevated blood pressure. It is known that, as a problem of blood cells, for example, lowered deformability of human red blood cells, an improvement in leukocyte adhesiveness, and exaltation in platelet aggregation activity lower blood fluidity.
Currently, pharmaceuticals for accelerating the metabolism of neutral fats or the cholesterol are available, however, satisfactory effects are not provided. Due to the fact that these are pharmaceuticals, there is also the problem of side effects. As with the foods derived from Physalis angulata L. according to Japanese Patent Laid-Open No. 143324/1986 for improving the levels of blood pressure and blood sugar, there has been a report on foods having a function of relaxing vasoconstriction and dilating peripheral vessels. However, temporary relaxation of vasoconstriction only provides a temporary solution and would conversely lead to deterioration of peripheral vessels. Thus, foods which would affect blood itself to improve its fluidity, thereby preventing diseases such as elevated blood pressure, cerebral hemorrhage, and coronary artery disease, have long been sought.
Conventional substances having a function for improving blood fluidity include the following pharmaceuticals. Japanese Patent Laid-Open No. 43436/1999 describes tocopherol phosphoric ester as a preventive and a therapeutic agent for peripheral vascular flow disorder. Japanese Patent Laid-Open No. 77328/1987 describes anthocyanin or anthocyanidin derived from crown of thorns, as a circulation-improving-agent which has a function of dilating blood vessels which acts as a diuretic, and acts to dilate coronary vessels, and improving cerebral circulation.
Japanese Patent Laid-Open No. 147523/1998 describes pharmaceuticals or foods containing a γ-linolenic acid as an active ingredient which acts to improve blood fluidity. The invention according to the above-described publication is carried out using equipment to directly measure blood fluidity as with the process adopted by the present inventors. This equipment enables direct observation and measurement of the condition of blood fluidity under a CCD camera by employing MC FAN KH-3 (Hitachi Haramachi Electronics Co., Ltd.). According to the examples of the publication, however, the efficacy of γ-linolenic acid is attained by administration thereof for two months to patients undergoing a dialysis treatment, and the γ-linolenic acid is used pharmaceutically.
Japanese Patent Laid-Open No. 81220/1991 describes a reduction of permeability of ciliary vessels by anthocyanidin. This is a pharmaceutical employed for treating diseases in peripheral vessels and is mainly related to effects on blood vessels. Conventionally, there is no description regarding the effects of anthocyanin or anthocyanidin on, for example, erythrocytes, leukocytes, and platelets in blood. There is no description regarding black currant, either.
On the other hand, known conventional foods for improving blood fluidity, include encapsulated foods according to Japanese Patent No. 2801990 which are provided by the addition of at least one member selected from the group consisting of an edible fatty oil, vitamin E, and lecithin to lipids surrounding the internal organ of Laticauda semifasciata. However, this patent is limited to encapsulated foods and not applicable to other types of foods. Also in this patent, a process is adopted wherein renal plasma flow is measured by a paraaminohippuric acid process to estimate the function of peripheral vessels. Effects thereof are limited to a function of improving peripheral blood fluidity.
Japanese Patent Laid-Open No. 112077/1996 describes that compositions for health foods derived from chitosan and a ginkgo leaf extract are effective in improving peripheral blood fluidity in the brain although there is no detailed description. Also, Japanese Patent Laid-Open No. 257866/1998 describes a health food comprising myo-inositol and the ginkgo leaf extract therein although detailed study thereof is not additionally described.
Japanese Patent Laid-Open No. 287576/1998 describes that a saffron extract acts to improve peripheral blood stream. Peripheral resistance of the blood stream is measured using a chart of Korotkoff's sounds and the effect thereof is limited to an effect of improving peripheral blood fluidity.
As described above, in the field of these foods, there has been no description on black currant anthocyanin in relation to blood fluidity improvement effect or blood pressure lowering effect.
In addition, administration of pharmaceuticals enables temporary recovery in visual function improvement effect, blood fluidity improvement function, blood pressure lowering function, etc. However, this does not relieve chronic symptoms. Therefore, substances have been desired in which visual functions, blood fluidity, and blood pressure are improved through the routine ingestion of foods. As described above, the content of black currant anthocyanin in black currant is in a very small quantity of not more than about 0.7% by weight on the basis of solid matters. Thus, foods containing a large quantity of black currant anthocyanin have not existed. Therefore, strongly desired was a black currant anthocyanin material, which can be added to foods in a large quantity. The process of the present invention provides a highly concentrated anthocyanin composition, which can be added to foods. This enables the addition of a large quantity of black currant anthocyanin to general foods. The present invention enables, for the first time, the routine ingestion of foods to improve visual function, foods to improve blood fluidity, or foods that function to lower blood pressure, respectively containing a large amount of black currant anthocyanin. According to the present invention, pharmacological functions of black currant anthocyanin, for example, prevention of chronic visual function deficiency and the like, effects in improving visual function, or a function for improving blood fluidity, and a function for lowering blood pressure are continuously realized by ingesting anthocyanin as foods.
Unexpectedly, the highly concentrated anthocyanin composition according to the present invention, unlike conventional fruit juice, has excellent stability and thus, is able to be stored for a long period of time when employed in drinks such as juice.